Mercer County Engineer's Office

Design Process

In order for a structure to be eligible for replacement, a number of things have to occur: 

The bridge must have a current inspection, and it's sufficiency rating must be less than 50%.

The bridge must be listed in a legislative "Bridge bill".

The bridge must be listed in both the Long range plan recommended by the MPO, and it must appear on the State 12 Year Transportation program.

In order for design to begin, at least the design phase must appear in the first 4 year period of the 12 year program.

Once these criteria are met, we submit a request for a design reimbursement agreement to the Pennsylvania Department of Transportation. The agreement must be prepared and executed before design work may begin.

 We research the property records for the area surrounding the bridge, and send notifications to the property owners of our intent to enter upon their property to obtain survey information. Our office conducts the field survey of the project area. The survey information is used to prepare a site plan for the area, and it is used throughout the design process.

 At this stage, we will make initial contacts with several State and Federal agencies:

Pennsylvania Department of Environmental Protection - A Pennsylvania Natural Diversity Inventory search is requested to determine if there are any "State threatened or endangered" plant species of special concern within the area that may be impacted by the project.

 U.S. Fish & Wildlife Service - This agency reviews the site to determine if any "Federally threatened or endangered" flora or fauna are known to exist in the project area.

 Pennsylvania Game Commission - This agency reviews the site to determine if any "State threatened or endangered" birds and mammals are known to exist in the project area.

 Pennsylvania Fish & Boat Commission - This agency reviews the site to determine if any "State threatened or endangered" fish, reptiles, and amphibians are known to exist in the project area.

 Pennsylvania Historical & Museum Commission - This agency reviews the project to determine if the structure is eligible for listing in the National Register of Historic Places, or if the project will impact an eligible property. They also review the site to determine if any archaeological investigations are required.

 If we are lucky, there won't be any endangered species, the bridge won't be historic or an historic type, and archaeological investigations won't be required. If we are not lucky, add a couple of years to the timetable and thousands of dollars of additional costs to address these concerns.

 Next, we will hire a "Wetlands specialist" to prepare a wetlands investigation and delineation in the area of the structure. This report is used in design to either avoid or minimize the wetlands impact in our preliminary design. With the broad definition of wetlands used in Pennsylvania today, all of our projects now involve wetlands to some extent.

 A Hydrologic and Hydraulic study is undertaken to determine the waterway opening of the replacement structure. An Erosion and sedimentation control plan is also prepared. The E & S plan is reviewed and approved by the County Conservation District, and this plan along with the H & H report is submitted to DEP to obtain a waterway permit. The township secretary will receive an Act 14 municipal notification letter prior to our submission to DEP.

 An environmental study is undertaken early in the project. Regional and community growth, Conservation and preservation, Public facilities, Community cohesion, Potential displacements, Air quality, Noise, Water pollution, Hazardous waste sites, Aesthetics, Maintenance, and Traffic are studied and addressed in the environmental document. The level of detail required is governed by the degree of impact to any of these areas.

 All known utilities will be provided with a site plan. They are requested to verify the location of their facilities within the project area, and indicate if they intend to locate facilities on the new structure.

 Once our structure size has been determined and approved in the waterway permit application stage, we begin a study of different types of structures for the site. Typically, we will evaluate a minimum of three different types and prepare cost estimates and cost benefit studies to determine the most economical structure. This information is assembled into a TS&L report and submitted to PennDOT for review and approval. This report shows the proposed type of structure, it's size both in waterway opening and clear roadway width, and it's location in relation to the existing structure.

 Most of our replacement structures will not involve a major change in alignment. This means if there is presently a curve at the site, it may be improved, but most likely it will not be eliminated. Likewise, only a minimal amount of approach roadway work will be undertaken. Since the funds are provided for bridge improvement and not roadway improvement, only the amount of approach work necessary to transition from the new bridge width to the existing roadway width is a permissible expenditure.

 A foundation investigation and core boring program is undertaken next. A state approved drilling contractor is hired to obtain soil and rock samples at the site. A geotechnical engineer will analyze the samples and prepare a foundation report which recommends the type of foundation required to support the proposed bridge. Their report will assign an allowable bearing capacity or allowable pile loads to be used for design. This report, like the TS&L report is submitted to PennDOT for approval.

 A design field view submission is next prepared and submitted to PennDOT. This submission includes details of the proposed roadway profile and alignment, and the proposed right of way takes.

 After design field view approval, we know the amount of land required to construct the project. Initial contacts are made to the property owners if additional right of way is required. They are provided with a right of way plan, a listing of the amount of area we need for the project, and a booklet explaining their rights under the law. In most of the cases, the amount of right of way required is small, and we request their consideration of donating the right of way. If they are not agreeable to a donation, our appraiser then prepares an appraisal to determine the fair market value so that an offer of compensation may be made. In Mercer county, our county solicitor is responsible for right of way negotiations with the property owners.

 Once our TS&L and foundations have been approved, we are ready to start the final design for the new bridge. The bridge design "bible" is the Standard Specifications for Highway Bridges published by the American Association of State Highway and Transportation Officials. This publication contains the general criteria that all bridges in the United States must adhere to. PennDOT also has a Design manual that supplements the AASHTO manual.

 Design calculations are made for all elements that make up the structure, and sketches are given to the CADD operator to prepare the working drawings required to build the structure. Our office has been working with a CADD, or computer aided design and drafting program since 1986. This has enabled us to reduce our drafting staff and still maintain the same productivity.

 Once the bridge drawings are completed and design calculations and quantities are finalized, a final bridge design submission is made to PennDOT for approval. PennDOT's reviews are required in each of these stages if any federal or state funds are involved, including our liquid fuels tax funds. PennDOT is required to certify to FHWA that the projects were prepared in compliance with all federal requirements.

 If right of way has not been cleared by this point, we request the solicitor complete negotiations and record the deeds. Generally, an amicable settlement is reached. If a settlement can not be agreed upon, then condemnation proceedings are started.

 The approach roadway transition drawings are also finalized at the same time we are finalizing our bridge drawings. These drawings are submitted to PennDOT and undergo a safety review.

 Final utility meetings are also held to coordinate any required relocations or structure attachments with the utilities.

 A final plan check is scheduled with PennDOT to review the final roadway and structure plan prior to preparation of the specifications package. On federal aid projects, the FHWA area engineer will participate in the review. They will review general plan content and any type of plan elements that may have caused problems in the past.

 The proposal package contains a set of the drawings and a set of written specifications the contractors must bid on. Although PennDOT has a standard set of specifications (the 408), individual specifications must be written to address areas that do not conform to the standards. Final cost estimates are also prepared at this stage as well as a draft advertisement. All of these are assembled into one final PS&E or plans, specifications and estimate package and submitted to PennDOT for final approval and authorization to advertise.

 The county commissioners will adopt a resolution for replacement of the structure and will authorize advertisement at one of their commissioners meetings.

 After the project is advertised and bids are received, they are opened and read at a commissioners meeting. Bids are reviewed to assure all bid conditions have been met, and the unit prices and totals are verified. Checks are made that the contractors are prequalified and that they are not currently debarred. If the bids are within the estimate range, a tabulation of bids is prepared and submitted to PennDOT along with a recommendation for award. Once PennDOT concurs with the award, the project bid is accepted and awarded at a commissioners meeting.

 We then prepare the construction contract for execution by the county and the contractor. After the contract is signed, a preconstruction conference is scheduled with the contractor, the utility companies, and other affected parties to review and coordinate the project schedule and to finalize the construction start date.

 Finally, after all of this, we are ready to move some dirt and start construction.